This invention relates to a liquid-cooled internal combustion engine and more particularly to an improved cooling arrangement for such engines that will reduce the likelihood of quenching in localized areas and will promote more uniform cooling around all combustion chambers of the engine.
The use of liquid-cooled internal combustion engines is well known. These engines are formed with cooling jackets in their major components, such as the cylinder block and/or cylinder head, and liquid is circulated through these cooling jackets for cooling the engine. In order to provide a simpler construction, the coolant is delivered into the engine through a main coolant inlet port. The internal portions of the engine are appropriately configured so that the coolant will flow from this inlet to a discharge outlet where it is passed through a heat exchanger for cooling and returned to the engine.
Frequently, the coolant inlet is disposed so that the coolant will flow against a surface of the engine which forms the combustion chamber. Although this can promote good cooling, it can also result in localized quenching of an area of the combustion chamber which can be undesirable. This is particularly true when the area of the casting that forms the combustion chamber is plated for wear resistance or other purposes.
The quenching operation, in addition to inhibiting effective combustion, can cause temperature gradients that cause internal stresses. Where the material is plated, this can, in fact, cause the plating to separate from the base material. These problems are particularly acute when very thin wall or film type plating is employed.
It is, therefore, a principal object of this invention to provide an improved cooling arrangement for a liquid-cooled internal combustion engine wherein the cooling system can be maintained relatively uncomplicated, but wherein localized quenching in the area of the coolant inlet is avoided.
As has been already noted, the cooling jacket of the engine is formed by cooling jackets in its major components, such as the cylinder block and cylinder head. It is the normal practice to introduce the coolant to either the cylinder block or the cylinder head, cool the casting to which the coolant is introduced, and then circulate it to the other casting's cooling jacket.
Normally the cylinder block and cylinder head cooling jackets communicate with each other with passages that are formed in the mating surfaces around the combustion chamber. These passages serve two purposes. First, they obviously permit the coolant to interchange between the cylinder head and cylinder block. In addition, these passages form exits through which the sand of the core of the casting can be removed after the cylinder block and cylinder head are cast. For this latter reason, it is desirable to maintain relatively large openings so as to ensure complete removal of the sand of the core.
However, it is also generally the practice to introduce the coolant at one end of the engine and discharge it from the other end of the engine. Usually the coolant is introduced at one end of the cylinder block and discharged at an opposite end of the associated cylinder head. As noted, the coolant flows between the cylinder block and cylinder head through openings formed in their mating surfaces, and these openings are relatively large.
Because of this arrangement, the flow of coolant through the casting in which the coolant is first introduced may not be uniform. That is, the coolant may flow adjacent the combustion chamber where the water is introduced and then directly into the other casting without having adequate flow through the remaining areas surrounding the combustion chamber and the casting in which the water is introduced.
It is, therefore, a further object of this invention to provide an improved arrangement for ensuring uniform cooling of all combustion chambers of the engine, even though the coolant may be introduced in a localized area at one end of the engine.